The present invention relates to a thermally processed image forming material less causative of adhesion in a form of commercial product.
A strong need for reducing the volume of waste process solution has arisen in recent field of printing from viewpoints of environmental preservation and space saving. Thus a recording material requiring no conventional step for solution development, fixation nor water washing is desired.
A thermally processed image forming material for producing photographic image based on heat development is disclosed, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075 and xe2x80x9cThermally Processed Silver Systemsxe2x80x9d written by D. Morgan and B. Shely, Imaging Processes and Materials, Neblette""s 8th ed., edited by Sturge, V. Walworth and A. Shepp, Item 2 (1989). Such thermally processed image forming material is hopeful of applications in various fields for the advantages of its mono-sheet constitution and development only by a heat processing.
The image recording material based on the heat development process is generally developed at 80 to 150xc2x0 C., so that when the material is intended for use in printing purpose, using gelatin as a binder as being practiced in the conventional photographic photosensitive material, will raise a problem that a significant dimensional change may occur due to shrinkage of the gelatin. While such dimensional change has been suppressed to a level of no problem in the practical use by using a polymer binder not shrinkable by heat, there is occurring a new problem that the material in a product form of rolled sheet or stacked sheets may result in adhesion between the outermost layers when allowed to stand under high temperatures (for example, 30xc2x0 C. or above).
It is therefore an object of the present invention to solve the foregoing problems. That is, the present invention is to provide a thermally processed image forming material less causative of adhesion in a form of commercial product.
The present inventors found after extensive investigations for solving the foregoing problem that an thermally processed image forming material less causative of adhesion can be obtained by specifying binders used in the outermost layers on both planes of the material; which led us to propose the present invention.
That is, the present invention is to provide a thermally processed image forming material having on only one side of a support an image forming layer characterized in that the outermost layer on the same side with the image forming layer contains a binder different from that contained in the outermost layer on the opposite side of the support.
Preferred embodiments of the present invention include such that the binder contained in the outermost layer on the same side with the image forming layer and the binder contained in the outermost layer on the opposite side of the support have a common monomer composition to a degree less than 75 wt %; such that a ratio of an I/O value of the binder contained in the outermost layer on the same side with the image forming layer and an I/O value of the binder contained in the outermost layer on the opposite side of the support is within a range from 0.1 to 0.90, or within a range from 1.10 to 10; such that the binder contained in the outermost layer on the opposite side of the support has a softening point of 100xc2x0 C. to 250xc2x0 C.; such that the binder contained in the outermost layer on the opposite side of the support has a softening point higher than a glass transition point of said binder by 30xc2x0 C. or more; such that a ratio of a Vickers hardness of the binder contained in the outermost layer on the same side with the image forming layer and a Vickers hardness of the binder contained in the outermost layer on the opposite side of the support is within a range from 0.1 to 0.95, or within a range from 1.05 to 10; such that the binder contained in the outermost layer on the same side with the image forming layer or on the opposite side of the support contains a polymer latex in an amount of 50 wt % or more of the total binder; such that the outermost layer on the same side with the image forming layer or on the opposite side of the support contains a fluorine-containing surfactant; such that the outermost layer on the same side with the image forming layer or on the opposite side of the support contains a slipping aid; and such that the image forming layer contains an organic acid silver salt and a reducing agent.